There are many different methods for determining the specific location of a wireless communication device being used within a wireless communication system. These methods may be categorized as network-based, device-based, or hybrid. Hybrid methods utilize features of both network-based and device-based methods. The categories indicate where the primary steps of the location determination processes are accomplished. In hybrid and device-based methods, some of the processing steps necessary to determine the location are performed in the wireless communication device.
Some examples of hybrid and device-based location determination methods make use of Global Positioning System (GPS) satellite signals. In these methods, the device receives signals from GPS satellites and uses those signals to calculate the location of the device. In device-based GPS methods, the device receives the GPS signals and performs the GPS location calculation with no assistance from the network. In hybrid GPS methods, the device receives some information from the network to assist with the location determination process.
One example of a hybrid method is the Assisted GPS (A-GPS) method. In the A-GPS method, the device receives information regarding expected GPS satellite positions from the wireless communication network. The information provided by the network assists the device in acquiring the GPS satellite signals. This assistance reduces the complexity of the computational process which the device must perform to determine the location and often reduces the time necessary to complete the location computations.